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Topic Review (Newest First)

09-05-2012 08:51 PM

bigblockragtop

Yup that is probably true I had no problem and the fuel is no longer LL. I would just mix in a few gallons, like I said it does not go bad.

08-31-2012 07:03 PM

vinniekq2

100LL aviation fuel is horrible gas to use straight in a car.I didnt even like using it in my cessna.A mogas STC was $150.00 for small cessnas and all you got was a sticker saying you could use mogas.Buy fuel stabiliser or octane boost or racing gas,but dont use a lot of 100LL.

08-31-2012 11:18 AM

bigblockragtop

Quote:

Originally Posted by JohnBaker

I've never had to use 100 plus octane fuel in the past. The engine builder claims the following:

HOWEVER, IN DESIGNING YOUR OWN HIGH PERFORMANCE ENGINE, WE ARE NOT LIMITED TO HOLDING ALL THINGS EQUAL AND CAN COMBINE PROPERLY MATCHED COMPONENTS TO REDUCE AN ENGINES OCTANE REQUIREMENT EVEN WITH HIGHER STATIC COMPRESSION.

C) SINCE VALVE TIMING CONTROL DYNAMIC CYLINDER PRESSURE, WE CAN USE THE CAMSHAFT TO LOWER THE OCTANE REQUIREMENT. ENGINE DAMAGING DETONATION TYPICALLY OCCURS AT LOW RPM. THIS IS BECAUSE OF THE COOLING EFFECT FROM INCREASED CYLINDER ACTIVITY ABOVE 2,800RPM. THIS IS WHY WE USE CAMS WITH 240+ DEGREES DURATION @ .050" ON 110 LOBE CENTERS WITH 2,400 TO 2,800 STALL CONVERTERS TO SUCESSFULLY RUN ENGINES ON PREMIUM PUMP FUEL AT 11.0:1 COMPRESSION.

What I meant is plane fuel does not go bad like pump gas not so much the octane since you said you don't drive it often.

08-30-2012 10:58 PM

vinniekq2

yes, 34 total timing including advance and static,no vacuum. It ran really good at 36 but I did that by mistake when I pulled the distributor to check gear wear and forgot the timing light at home. I power timed it.

08-30-2012 10:42 PM

68NovaSS

Vinnie, you mean 34 total?

08-30-2012 10:35 PM

vinniekq2

a small correction for a typo,,
I run a combined total of 34 degrees,sorry if there was confusion.

and I had to replace my valve springs because of above mentioned problem of sitting too much.good luck with the car,I love/hate mine a lot.

08-30-2012 10:19 PM

JohnBaker

Quote:

Originally Posted by vinniekq2

degree wheel,,ok.22 thou is a tight lash cam,was more wondering if you had over tightened 1 or more valves.,,,
my compression is 10.75:1 and I have no pinging.I tuned my engine for 92 octane but some stations here still have 94,all with out methanol. when the car is running well,hopefully you accelerate briskly on occasion to keep things clean.I can drive at 2 000 rpm in o/drive with out issues,I use 035-040 plug gap.I run my car 1 quart low.
I run 24 degrees total advance,no vacuum,about 16 at idle,all in by 2800 rpm,,,I use a holley 950 and vic jr intake and big headers.

also of note, your valve springs may have gone soft from sitting long periods of time with out running,,,think about when you park the car at least 1 valve is wide open and how long you left it like that???

Those are all good points Vinnie and I appreciate them. I'm going to re-check valve settings and check to make sure the the right springs stop bushing are installed and not contributing to excessive timing advance. Try a set of new plugs as well and see where I am.

08-30-2012 09:34 PM

vinniekq2

degree wheel,,ok.22 thou is a tight lash cam,was more wondering if you had over tightened 1 or more valves.,,,
my compression is 10.75:1 and I have no pinging.I tuned my engine for 92 octane but some stations here still have 94,all with out methanol. when the car is running well,hopefully you accelerate briskly on occasion to keep things clean.I can drive at 2 000 rpm in o/drive with out issues,I use 035-040 plug gap.I run my car 1 quart low.
I run 24 degrees total advance,no vacuum,about 16 at idle,all in by 2800 rpm,,,I use a holley 950 and vic jr intake and big headers.

also of note, your valve springs may have gone soft from sitting long periods of time with out running,,,think about when you park the car at least 1 valve is wide open and how long you left it like that???

08-30-2012 08:37 PM

JohnBaker

Quote:

Originally Posted by vinniekq2

when you adjusted the cam lash,how did you do it?

Brought the engine to TDC and set the lash on

Intakes: 1257

Exhausts: 1348

Moved the engine 180 degrees and set the lash on:

Intakes: 3468

Exhausts: 2567

08-30-2012 08:28 PM

vinniekq2

when you adjusted the cam lash,how did you do it?

08-30-2012 05:41 PM

oldbogie

The fouled plugs could have been from the excess oil, or from an over rich mixture, or from too cold a heat range on the plug.

You've got an awful lot of compression for that cam. I compute a Dynamic Compression Ratio (DCR) of nearly 10 to 1 assuming 6 inch rods and only 7 ccs of volume in the piston crown for valve relief plus a zero deck block with a .030 head gasket. One usually looks to hit around a DCR of 8.5 to 8.8 with aluminum heads and 91 octane unleaded. The DCR is the Static Compression Ratio, in your case 11:1, then adjusting it for the piston position in the bore which is inches of lost stroke in crankshaft degrees for when the intake closes, Comp says 71 degrees ABDC at .0015 inch lift which still isn't completely closed but pretty darn close.

This cam wants more base (static) time than 10 degrees but this may be a reasonable compromise against the high DCR. Adding base timing must have a corresponding reduction in the variable timing in order to hold the maximum where the engine will tolerate it. If 34 is the upper limit of all timing and 10 degrees is in the base then the variables have to top out at 24 degrees. If the base timing is moved to 20 degrees (for an example) then the variables have to be limited to 14 degrees.
Detonation can be managed by reducing the amount of timing advance or slowing the rate at which it comes in. It is also controllable with a richer mixture, a cooler mixture, a cooler running temp, stiffer gearing, water/alcohol injection or lowering the compression ratio.
Generally a compromise between less or slower advance to manage detonation costs more power than compromising the compression ratio enough to quell the pinging. At least this is apparent at WOT/redline; but pinging tends to be present at mid RPMs due to excess advance for the power drain on the crankshaft (“lugging” could be a term here) and at WOT where everything is hot an heavy in the combustion chambers. The former is often excess advance but can be a bit of a lean mixture (both can happen a the same time for different reasons) the latter is most often a lean drop of the carb at WOT, this can often be an emulsion air correction issue as much as fuel jetting one. The safer route is to throw more fuel sooner. Messing around with air correction takes a lot of expertise and special, not to mention expensive, tools.

I really wouldn't think an additional quart of oil would cause plug fouling at least to the extent of your picture. This makes me suspicious that the pan may not have the parts needed to separate the flying oil and put it back in the sump. At a minimum the pan on an engine of this potential needs a very good windage tray or screen, an oil stripper on the right side of the crank to catch the flying oil and direct it down into the sump and a splash guard under the oil pump to keep oil from running up under acceleration and flooding the rear counter weight of the crank and the rear seal. Without a windage tray/screen and an oil stripper; the rings, especially if they are the ultra modern low pressure and thin cross section type, are just overwhelmed by the amount of oil that gets up on the cylinder walls. I'm also not a big fan of gapless second rings which quite a few builders use and your engine might have. If you get oil contamination from the valve guides, a Positive Crankcase Vent (PCV) or a leaking intake or head gasket, the oil gets trapped in the area between the second and top ring where the second ring cannot vent this stuff into the crankcase. Same goes with excess fuel. These conditions will show up as fouled spark plugs since this gunk has to ride around with the piston till it finds a way out with the exhaust by first contaminating the mixture.

Bogie

08-30-2012 05:28 PM

JohnBaker

Quote:

Originally Posted by bigblockragtop

I am not sure about the gap but 35 is where I used to keep mine. Oil can cause detonation too. I would try just changing the gas first. Do not forget there is also winter and summer formulas. So if you do not drive the car a lot you could have the wrong season gas in it. Also with the ethanol in gas it goes bad fast. If you don't drive it a lot put some stabilizer in it. Or what I did was used some 100 octane plane fuel. I know it is not totally recommended but if you do not drive the car a lot the plane fuel does not go bad. Drive that car letting it wit will kill it. At least get it up to temp once a month to get the contaminants out of the engine. Don't mess with the timing until you try the simple stuff first.

I've never had to use 100 plus octane fuel in the past. The engine builder claims the following:

HOWEVER, IN DESIGNING YOUR OWN HIGH PERFORMANCE ENGINE, WE ARE NOT LIMITED TO HOLDING ALL THINGS EQUAL AND CAN COMBINE PROPERLY MATCHED COMPONENTS TO REDUCE AN ENGINES OCTANE REQUIREMENT EVEN WITH HIGHER STATIC COMPRESSION.

C) SINCE VALVE TIMING CONTROL DYNAMIC CYLINDER PRESSURE, WE CAN USE THE CAMSHAFT TO LOWER THE OCTANE REQUIREMENT. ENGINE DAMAGING DETONATION TYPICALLY OCCURS AT LOW RPM. THIS IS BECAUSE OF THE COOLING EFFECT FROM INCREASED CYLINDER ACTIVITY ABOVE 2,800RPM. THIS IS WHY WE USE CAMS WITH 240+ DEGREES DURATION @ .050" ON 110 LOBE CENTERS WITH 2,400 TO 2,800 STALL CONVERTERS TO SUCESSFULLY RUN ENGINES ON PREMIUM PUMP FUEL AT 11.0:1 COMPRESSION.

08-30-2012 03:38 PM

bigblockragtop

I am not sure about the gap but 35 is where I used to keep mine. Oil can cause detonation too. I would try just changing the gas first. Do not forget there is also winter and summer formulas. So if you do not drive the car a lot you could have the wrong season gas in it. Also with the ethanol in gas it goes bad fast. If you don't drive it a lot put some stabilizer in it. Or what I did was used some 100 octane plane fuel. I know it is not totally recommended but if you do not drive the car a lot the plane fuel does not go bad. Drive that car letting it wit will kill it. At least get it up to temp once a month to get the contaminants out of the engine. Don't mess with the timing until you try the simple stuff first.

08-30-2012 03:25 PM

JohnBaker

Quote:

Originally Posted by 68NovaSS

11:1 is pushing it for pump gas. You need more initial timing, start with about 16 - 18, vacuum disconnected and plugged, and maximum 38 degrees, all in by 2500 or 3k. If you have detonation pulling a load, back total timing down in 2* increments until it goes away. Have you checked all around for a vacuum leak? You're definitely running rich, 800 cfm is a lot for a street 383, but doable with a good tune. I have the same heads on my Nova, using the same plugs. I used 3933's initially, but now use RC12's as well. Short drives around the neighborhood can be a problem with fouled plugs.

Slow typing, BBR mentioned some of these points too...

I have an advance timing light. 16-18 degrees is way off the timing tab. I have to read it by turning the knob on the light until my timing marks are matched. I hope this is the right method. incidentally, should I set the total timing first at 2500 RPMs and then leave the initial timing fall where it falls? Mind telling me the gap on your plugs? I figured with MSD ignition I could use a wider gap of .045. Do you think that's too much? I have checked for vacuum leaks and found none.

08-30-2012 03:18 PM

JohnBaker

Quote:

Originally Posted by bigblockragtop

Just my unproffessional 2 cents but 11-1 compression on a carbed car is on the edge even with 93 octane. Hard for me to tell if that is black from fuel or oil. Have you checked your air fuel ratio. Pop through the carb could be as simple as moisture under the cap. Hopefully it is not a valve sticking. Does it go away after warm up or maybe get worse. Have you opened it up and blown all the gunk out of it(carbon etc). Not driving is sometimes worse then driving every day.

I haven't taken it out on the freeway for fear of doing damage, but that might be the answer. I haven't checked the air fuel ratio. The Edelbrock 800 Performer Carb P/N 1413 is as is out of the box. Distributor cap is new and dry, as is the rotor.

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